The complete deduced amino acid sequences of legumin β-polypeptides from different genetic loci inPisum

The deduced amino acid sequences of the β-polypeptides ofPisum legumin from two loci on chromosome 1 were compared with one from a locus on chromosome 7. The chromosome 1-derived sequences were ∼80% identical, but each was only ∼50% homologous to the chromosome 7-derived sequence. Comparison of these sequences with those of homologous polypeptides from two other species of the Leguminoseae showed that the chromosome 1-derivedPisum sequences were more similar to legumin B than to legumin A fromVicia faba and were more closely related to group II than to group I glycinins fromGlycine max. The converse was true for the chromosome 7-derivedPisum sequences. This suggests that divergence of legumin-like sequences predated speciation in these three members of the Leguminosease.Among the threePisum sequence classes, a highly variable region was identified within the α-polypeptide, just to the amino-terminal side of the αβ processing site. This region varied considerably in length within the three classes ofPisum α-polypeptide sequence, a variation which far exceeded that which has previously been described for other legumins and glycinins. The chromosome 7-derived, and one of the chromosome 1-derived α-polypeptide sequences contained different tandem repeats in this region.